This application discloses an invention that is related, generally and in various embodiments, to a system and method for cooling a multi-cell power supply.
Multi-cell power supplies are known in the art. Such power supplies generally include a three-phase transformer and a plurality of power cells which are electrically connected to secondary windings of the transformer. Each power cell accepts three-phase AC input power from secondary windings of the transformer and outputs a single-phase AC voltage. The power connections between the secondary windings of the transformer and the power cells are realized with either bus or cable, and the bus or cable is either convection cooled or force cooled by air.
In multi-cell power supplies, the transformer and the power cells may be cooled with either air or water. For water-cooled applications, the individual power cells are typically cooled with a fluid stream that is separate from the fluid stream that cools the respective secondary windings of the transformer which supplies the power to the power cells. The water-cooled systems generally include a water supply manifold, a water return manifold, an individual hose from the water supply manifold to each power cell, an individual hose from the water supply manifold to each secondary winding of the transformer, an individual hose from the water return manifold to each power cell, an individual hose from the water return manifold to each secondary winding of the transformer, a water pump, and a water-to-air heat exchanger. As water flows through the secondary windings of the transformer and the power cells, heat is transferred from the secondary windings of the transformer and the power cells to the water. As the heated water flows through the water-to-air heat exchanger, heat is transferred from the water to the air passing over the water-to-air heat exchanger, thereby cooling the water.
Due to the parallel nature of the flow paths of the water, such cooling systems tend to be relatively expensive to manufacture and operate. The high number of hoses required for the above-described piping arrangement adds to the complexity and cost of the cooling system. With the parallel flow path arrangement, the required flow rate in gallons per minute (GPM) needed to effectively cool the secondary windings of the transformer and the power cells is inherently higher. As the cost of a water pump tends to be a function of the required flow rate, the cost of the water pump required for such a cooling system is relatively expensive.
In addition, the high flow rate results in a low temperature rise of the water when heat is transferred from the secondary windings of the transformer and the power cells to the water. When the heated water flows through the water-to-air heat exchanger, the relatively low temperature of the water due to the higher flow rate reduces the efficiency of the water-to-air heat exchanger, thereby decreasing the effectiveness of the cooling system.
Yet another drawback of conventional cooling systems is potential for leaks from either failed hoses or failed connections between the hoses and other components of the cooling system. For example, due to high water pressure required to achieve the necessary flow rate, fittings and hoses near the water pump may be subjected to high pressures and have a higher likelihood of failure. A water leak could lead to overheating of the power supply, or in the case where the water directly contacts the cells, cause a dangerous situation requiring immediate stopping of the power supply.
Still another drawback of conventional cooling systems is that the bus or cable connecting the secondary windings of the transformer to the power cells releases heat into the air inside the enclosure of the power supply, so that internal air-to-water heat exchangers must be supplied to transfer this heat into the water. The temperature of the internal air is increased by heat, which may adversely affect the local electronic circuits.